Waste heat transfer system for aircraft fuel cell

ABSTRACT

An aircraft has an aircraft propulsor and/or an aircraft propulsor drive. The aircraft propulsor and/or an aircraft propulsor drive acts as a waste heat source. The aircraft has a metal-air fuel cell. The aircraft has a waste heat transfer system configured to thermally couple the metal-air fuel cell and a waste heat source. The aircraft includes a control system configured to operate the waste heat transfer system to selectively transfer waste heat from the waste heat source to the metal-air fuel cell.

PRIORITY

This patent application claims priority from provisional U.S. patentapplication No. 63/272,031, filed Oct. 26, 2021, entitled, “ENERGYSTORAGE,” and naming Jeffrey Engler and Arthur Dobley as inventors, thedisclosure of which is incorporated herein, in its entirety, byreference.

FIELD

Illustrative embodiments of the invention generally relate to energystorage and, more particularly, various embodiments of the inventionrelate to energy storage for an aircraft.

BACKGROUND

Electric-propelled aircraft are powered by onboard energy storage. Theaddition of onboard energy storage increases weight to the aircraft, andthus decreases the useful load of the aircraft. Furthermore, certaintypes of energy storage, such as fuel cells, may increase in weight asthey are expended.

SUMMARY OF VARIOUS EMBODIMENTS

In accordance with one of the embodiments of the invention, an aircrafthas an aircraft propulsor and/or an aircraft propulsor drive. Theaircraft propulsor and/or an aircraft propulsor drive acts as a wasteheat source. The aircraft has a metal-air fuel cell and a waste heattransfer system to thermally couple the metal-air fuel cell and a wasteheat source. The aircraft also has a control system to operate the wasteheat transfer system to selectively transfer waste heat from the wasteheat source to the metal-air fuel cell.

In some embodiments, the aircraft has an air supply system to pressurizean air supply for the metal-air fuel cell.

In some embodiments, the aircraft has a plurality of metal-air fuelcells including the metal-air fuel cell and the waste heat transfersystem includes a diverter system to selectively transfer heat from thewaste heat source to a portion of the plurality of metal-air fuel cells.

The control system may determine a power output status of a firstmetal-air fuel cell of the plurality of metal-air fuel cells, andoperate the diverter system to transfer waste heat from the waste heatsource to the first metal-air fuel cell in response to determining thepower output status. The waste heat may then evaporate an electrolyte ofthe first metal-air fuel cell.

The control system may determine at least one of a power output statusor a temperature of one of the plurality of metal-air fuel cells, andoperate the diverter system to transfer heat from the waste heat sourceto a first metal-air fuel cell in response to determining the at leastone of the power output status or the temperature.

The control system may determine a take-off event is occurring andoperate a diverter system to transfer heat from the waste heat source tothe metal-air fuel cell in response to determining the take-off event isoccurring.

In some embodiments, the waste heat transfer system includes aliquid-to-liquid heat exchanger, a liquid-to-air heat exchanger, and adiverter system, and the metal-air fuel cell is an aluminum-air fuelcell.

In accordance with another embodiment of the invention, a method forheating a metal-air fuel cell includes operating an aircraft including awaste heat source and a metal-air fuel cell. The method then outputspower from the metal-air fuel cell. The method then generates thrust andwaste heat using the waste heat source. The method then transfers thewaste heat to the metal-air fuel cell.

In some embodiments, the method pressurizes an air supply and providesthe pressurized air supply to the metal-air fuel cell.

In some embodiments, the method determines at least one of a poweroutput status or a temperature. Transferring the waste heat to themetal-air fuel cell may be in response to determining the at least oneof the power output status or the temperature.

The aircraft may include a second metal-air fuel cell. In someembodiments, the method determines a power output status of the secondmetal-air fuel cell and transfers at least a portion of the waste heatto the second metal-air fuel cell.

The method may determine a power output status of the metal-air fuelcell and evaporate an electrolyte using the waste heat of the metal-airfuel cell.

In accordance with yet another embodiment of the invention, an aircraftincludes an aircraft propulsor and/or an aircraft propulsor drive, theaircraft propulsor and/or an aircraft propulsor drive acting as a wasteheat source. The aircraft includes two metal-air fuel cells to providepower to the aircraft propulsor drive. The aircraft includes a wasteheat transfer system to thermally couple the first and second metal-airfuel cells and a waste heat source. The aircraft also includes a controlsystem to operate the waste heat transfer system to selectively transferwaste heat to the first metal-air fuel cell and the second metal-airfuel cell.

The first and second metal-air fuel cells may be aluminum-air fuelcells.

In some embodiments, the waste heat transfer system includes a heaterexchanger and a diverter system including a plurality of valves, whereinthe control system is to operate the plurality of valves to selectivelytransfer the waste heat to the first metal-air fuel cell, and then tothe second metal-air fuel cell.

The control system may determine a power output status for the firstmetal-air fuel cell and evaporate an electrolyte of the first metal-airfuel cell in response to the power output status.

The aircraft may include an air supply system to pressurize an airsupply for the first and second metal-air fuel cell.

The control system may determine a take-off event is occurring andoperate a diverter system of the waste heat transfer system to transferheat from the waste heat source to the first metal-air fuel cell inresponse to determining the take-off event is occurring.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art should more fully appreciate advantages ofvarious embodiments of the invention from the following “Description ofIllustrative Embodiments,” discussed with reference to the drawingssummarized immediately below.

FIG. 1 schematically shows an aircraft having an exemplary energystorage in accordance with various embodiments.

FIG. 2 schematically shows an energy storage in accordance with variousembodiments.

FIG. 3 schematically shows a metal-air fuel cell in accordance withvarious embodiments.

FIG. 4 shows a process for diverting waste heat in according to variousembodiments.

FIG. 5 shows a process for reducing aircraft weight in accordance withvarious embodiments.

FIG. 6 shows a process for powering an aircraft during take-off inaccordance with various embodiments.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In illustrative embodiments, an aircraft is propelled by electricpropulsors powered by metal-air fuel cells. The fuel cells may besupplied with pressurized oxygen and/or waste heat derived from anonboard heat source to increase the power density of the cells. Detailsof illustrative embodiments are discussed below.

FIG. 1 schematically shows an aircraft 100 in accordance with variousembodiments. Among other things, the aircraft 100 may be able to carry90-150 passengers on flights at jet altitudes and speeds over distancesof at least 600 miles.

The aircraft 100 may have a fuselage 102, which may house a pressurizedpassenger area 106 configured to house passengers and providepressurized air to passengers. The fuselage 102 may further house anunpressurized area 104 for storing cargo. The aircraft 100 may have oneor more sets of wings 108 configured to provide suitable lift forflight, takeoff, and landing.

The aircraft 100 has an energy storage 110 configured to store andprovide power to propulsor drives 103 configured to invert power fromthe energy storage 110. The propulsor drive 103 provides the invertedpower to the electric propulsors 101 configured to generate thrust.Among other things, the propulsor 101 may have a power rating of atleast 2 MW. The propulsors 101 may be coupled to the wings 108, the tail107, or the fuselage 102.

A byproduct of generating thrust using electric power is heat, alsoknown as waste heat. Each propulsor 101 and propulsor drive 103 is awaste heat source. Energy storage 110 is configured to use the wasteheat from a propulsor 101 or propulsor drive 103 as a waste heat source,to increase the output power capabilities of the energy storage 110.While waste heat sources are located on the wing in the illustratedaircraft 100, some waste heat sources, such as propulsor drives, may berelocated into the fuselage in some embodiments.

The energy storage 110 has aluminum-air fuel cells 120 configured tostore and output power. The aluminum-air fuel cells 120 may beaggregated into fuel cell packs secured in the aircraft 100, such as inthe pressurized area 106 or the unpressurized area 104. The aluminumair-fuel cells 120 may be located in the cargo hold of the unpressurizedarea. Since an aluminum fuel cell is a primary cell, the fuel cellspacks, the aluminum-air fuel cells 120, or at least the aluminum withinthe fuel cells 120, is removable and may be replaced when expended. Itshould be appreciated that the number of illustrated aluminum air fuelcells is not intended as a limitation. In some embodiments, the aircraftmay include more or fewer aluminum air fuel cells 120. In someembodiments, the aluminum-air fuel cell may instead be another metal-airfuel cell, such as zinc, among other things.

The energy storage 110 has a waste heat transfer system 130 configuredto thermally couple at least one waste heat source to the aluminum-airfuel cells 120. The waste heat generated by the waste heat source may beselectively provided to the aluminum-air fuel cell 120 to change certaincharacteristics, such as increasing power density and decreasing weight.

FIG. 2 schematically shows the energy storage 110 configured to receiveheat from a waste heat source 105 in accordance with variousembodiments. In the illustrated embodiment, the energy storage 110 hasfuel cell packs 125 comprising the aluminum-air fuel cells 120. Amongother things, each fuel cell pack 125 may include 50-100 aluminum-airfuel cells 120. In some embodiments, the heat transfer system 130 mayselectively provide heat to individual aluminum-air fuel cell 120 ratherthan selectively providing heat to aluminum-air fuel cells 120 of one ofthe fuel cell packs 125.

It should be appreciated that the topology of energy storage 110 isillustrated for the purpose of explanation and is not intended as alimitation of the present disclosure. For example, the energy storagemay include more or fewer heat exchangers, more or fewer valves, more orfewer pumps, or a rearrangement of any of the illustrated components.

The energy storage 110 includes circulating lines 214 configured tocirculate a liquid through the waste heat source 105, valves 211 and212, liquid-to-heat exchanger 210, heat exchanger 220, and pump 213. Theliquid circulated through the circulating lines 214 is configured toabsorb waste heat from the waste heat source 105, and transfer the wasteheat to heat exchanger 210 or the heat exchanger 220, depending on theconfiguration of the valves 211 and 212. The valves 211 and 212 may beopened, closed, or partially opened. The pump 213 is configured tocirculate the liquid through the circulating lines 214. Theliquid-to-air heat exchanger 210 is configured to disperse excess heatthat is not needed or cannot be used by the energy aluminum-air fuelcell 120. In some embodiments, the control system 260 controls thevalves 211 and 212 based on a temperature of the aluminum-air fuel cells120. In some embodiments, the control system 260 partially opens thevalves 211 and 212 to simultaneously transfer heat to the fuel cells 120and disperse excess heat.

The heat exchanger 220 is configured to transfer heat between the liquidin circulating lines 214 and the liquid in circulating lines 221. Thecirculating lines 2201 are configured to circulate a liquid through pump223; valves 234, 235, and 236; and heat exchangers 251, 253, and 254,depending on the configuration of the valves 234, 235, and 236. Byopening, closing, or partially opening one or more of the valves 234,235, and 236, the control system 260 can select which heat exchanger theliquid circulates through, and thereby selects which of the aluminum-airfuel cells receives the waste heat. By having the circulating lines 221,the liquid in the circulating lines (i.e., oil) does not circulate inthe same heat exchanger as the electrolyte circulating in the cell packs125, and may also reduce the amount of electrolyte and oil needed forthe waste heat transfer system 130.

The diverter system 240 system of the energy storage 110 is comprised ofcontrollable devices configured to allow or block the flow of liquidthrough circulating lines. In the illustrated example, the divertersystem 240 includes valves 211, 212, 234, 235, and 236. In this way, thediverter system 240 is configured to selectively transfer waste heatfrom the waste heat source 105 to one or more of the aluminum-air fuelcells 120 or cell packs 125 at one time. In some embodiments, the fuelcell packs are located on racks that integrate the heat exchangers 251,253, and 254, or valves 234, 235, and 236, or a combination thereof.

The power density of metal-air fuel cell is dependent in part on thetemperature of the fuel cell. The power density of the fuel cellgenerally increases as the temperature of the fuel cell increases, up tothe boiling point of the electrolyte. The control system 260 isconfigured to operate the diverter system 120 to heat an aluminum-airfuel cell 120 outputting power or preparing to output power to maximizethe power density of the fuel cell 120. The control system 260 monitorsthe temperature of the fuel cell 120 to avoid the boiling point of theelectrolyte. Since the aircraft 100 climbs to high altitudes, theboiling point of the electrolyte may be affected by the reduceatmospheric pressure. Therefore, the control system 260 is configured todetermine the fuselage pressure where the fuel cells 120 are located inthe fuselage (e.g. using a barometric sensor) and adjust the waste heatprovided to the fuel cell 120 to not exceed the changing boiling point.For example, as the aircraft 100 flies higher, temperature threshold ofthe fuel cell must be lowered to account for the lowering boiling pointof the electrolyte. In some embodiments, the control system 260determines the fuel cell temperatures using sensors configured tomeasure the electrolyte temperature, among other things. If the wasteheat source produces too much waste heat, the control system dispersesthe excess heat external to the aircraft 100 using heat exchanger 210.The control system 260 may determine to transfer heat to one or more ofthe fuel cells based on the temperature of the battery, the state ofcharge of the fuel cell, or the amount of heat being generated by theaircraft 100, all of which may be measured by various sensors and othermeasuring devices.

Once the fuel cell 120 is expended and no longer capable of providingpower, the control system 260 may then apply heat so that theelectrolyte exceeds the boiling point and evaporates, thereby reducingthe weight of the fuel cells 120.

FIG. 3 schematically shows the aluminum-air fuel cell 120 in accordancewith various embodiments. The aluminum-air fuel cell 120 generates powerthrough a chemical reaction between aluminum and oxygen. To that end,the aluminum-air fuel cell 120 of FIG. 3 includes an aluminum anode 301and a cathode 311 separated by an electrolyte chamber 303 filled with anelectrolyte 305. The aluminum anode 121 may be comprised of aluminum oran aluminum alloy. Among other things, the aluminum anode 121 may becomprised of an aluminum-magnesium alloy or an aluminum magnesium-tinallow.

The electrolyte 123 may be comprised of an alkaline material and asolvent. For example, the electrolyte 123 may be comprised of potassiumhydroxide (KOH) and water, among other things. When the electrolyte 305is evaporated by the waste heat, the solvent evaporates while thealkaline material may not. The electrolyte circulator 320 circulates theelectrolyte 305 in the electrolyte chamber 303 and may heat theelectrolyte when passed through the heat exchanger of the electrolytecirculator 320.

The fuel cell 120 includes a separator 307 configured to allow air intothe electrolyte chamber 303 while preventing the electrolyte fromescaping from the electrolyte chamber 303.

The fuel cell 120 includes a current collector, such as a nickel mesh.The fuel cell 120 also includes a cathode 311 including carbon and acatalyst. The carbon may support the catalysts and the catalysts mayinclude, platinum, or manganese dioxide, among other things.

The energy storage 110 also has fuel cell support systems configured toassist the aluminum-air fuel cell 120 with outputting power. To thatend, the fuel cell support systems include an air supply system 330configured to provide oxygen to the fuel cell 120. In certainembodiments, the air supply system 330 includes an air compressor thatpressurizes the air before providing the air to the aluminum-air fuelcell 120. At high altitudes, the oxygen content of the air decreases. Bypressurizing the air, the air compressor increases the oxygen providedto the aluminum-air fuel cell 120.

The fuel cell support systems also include an electrical interface 340configured to receive power output by the aluminum-air fuel cell 120.The fuel cell support systems 140 further include an electrolytecirculator 320, configured to circulate the electrolyte of thealuminum-air fuel cell 120. The electrolyte circulator 143 may include apump 321 and a heat exchanger 323.

The aluminum-air fuel cells 120 have a maximum power rating and anenergy storage rating determined by the aluminum anode 301.Specifically, the more aluminum anode mass in the fuel cell 120, thehigher the energy storage rating. The greater the surface area of thealuminum anode 121 in the fuel cell 120, the higher the maximum powerrating.

In some embodiments, the aircraft 100 includes fuel cells havingdifferent configurations of the aluminum anode 121 to satisfy bothenergy and power requirements. These configurations may be referred toas energy cell configuration and power cell configuration.

In the energy cell configuration, the aluminum anode 301 may be a blockof solid material. By contrast, in the power cell configuration, thealuminum anode 301 may be comprised of an aluminum foam to increase thesurface area while maintaining similar outer dimensions to the blockused in the energy cell configuration. In some embodiments where thepower cell configuration and the energy cell configuration have equalouter dimensions, the mass of aluminum in the power cell configurationmay be less than half the mass of the aluminum in the energy cellconfiguration, to name but one example. By using a foam instead of asolid material, the maximum output power for the power cellconfiguration may be at least 3 times the maximum output power where ablock of similar dimensions is used.

Unlike other applications of fuel cells, the flights of the aircraft 100will have a similar power curve: a maximum power demand as the aircraft100 ascends to cruising altitude, a reduced power demand as the aircraft100 travels at cruising speed, and a further reduced power demand as theaircraft 100 descends and lands. When the aircraft 100 includes fuelcells with both energy cell configuration and power cell configurations,the control system 260 may advantageously use the power cellconfiguration fuel cells to achieve the maximum power output requiredduring take-off, thereby avoiding the need for the aircraft 100 to carryadditional fuel cells not needed to meet an energy storage capability inorder to achieve the maximum power output required for take-off.

FIG. 4 shows an exemplary process 400 for diverting waste heat of theaircraft having the energy storage 110 including more than one fuel cellin accordance with various embodiments. A number of variations ormodifications to Process 400 are contemplated including, for example,the omission of one or more aspects of Process 400, the addition offurther conditionals and operations, or the reorganization or separationof operations and conditionals into separate processes.

Process 400 begins at operation 401 where the control system 260determines the power output status of one of the aluminum-air fuel cells120. Power output status may include, among other things, a voltage ofoutput power, a current of output power, a received command tobegin/stop outputting power from a fuel cell, or a state of charge ofthe fuel cell. For example, the control system 260 may determine thatone of the aluminum-air fuel cells 120 is expended, or the controlsystem 260 may determine that one of the aluminum-air fuel cells 120 hasbegun outputting power to the aircraft 100. Determining the power outputstatus may include determining a change in the power output status.Where the power output status indicates a change of the fuel cellsupplying power to the aircraft 100, Process 400 will proceed tooperation 403 to begin providing waste heat to the new aluminum-air fuelcell, and decrease or terminate providing waste heat to the previousaluminum-air fuel cell 120.

During operation 403, the control system 260 determines a prescribedtemperature for the aluminum-air fuel cell 120. The prescribedtemperature may be the temperature that increases or maximizes the powerdensity of the aluminum-air fuel cell 120, among other things.

The control system 260 begins to heat the new aluminum-air fuel-cell 120in operation 405 by operating the diverter system 240 to divert thewaste heat, at least in part, to the new aluminum-air fuel-cell 120.

In operation 407, the heated aluminum-air fuel-cell 120 provides outputpower to the propulsors of the aircraft 100. The increased temperatureof the aluminum-air fuel-cell 120 increases the power density of thealuminum-air fuel cell 120.

It should be appreciated that Process 400 may be repeated each time thecontrol system 260 selects a new fuel cell 120 to provide power afterthe previous fuel cell has been expended.

FIG. 5 shows an exemplary process 500 for reducing aircraft weightduring flight in accordance with various embodiments. A number ofvariations or modifications to Process 500 are contemplated including,for example, the omission of one or more aspects of Process 500, theaddition of further conditionals and operations, or the reorganizationor separation of operations and conditionals into separate processes.

Process 500 begins at operation 501 where the control system 260determines that a power output status for the aluminum-air fuel-cell 120indicates the fuel-cell has been expended. In order to continue toprovide power to the aircraft 100, the control system 260 selects a newaluminum-air fuel cell 120 to output power. In operation 503, thecontrol system 260 determines a prescribed temperature for the expendedaluminum-air fuel-cell 120 based on the inflight boiling point of theelectrolyte 305. The control system 260 diverts the waste heat to theexpended aluminum-air fuel-cell 120 to heat the fuel cell 120, causingthe solvent of the electrolyte to begin evaporating. The control system260 continues to heat the aluminum-air fuel-cell 120 based on theprescribed temperature. After the control system 260 determines, inoperation 507, an electrolyte status, i.e., that either all of theelectrolyte, or a prescribed portion of the electrolyte has evaporated,the control system, in operation 509, diverts the waste heat from theexpended aluminum-air fuel cell 120.

By evaporating the solvent (i.e., water) of the electrolyte 305 andexhausting the vapor from the aircraft 100, the mass of the electrolyteis removed from the aircraft 100. Evaporating may be preferred overdraining the electrolyte 305, since the alkaline material of theelectrolyte 305 may be toxic, and may need to be treated before beingreleased from the aircraft 100.

FIG. 6 shows an exemplary process 600 for powering an aircraft duringtake-off in accordance with various embodiments. A number of variationsor modifications to Process 600 are contemplated including, for example,the omission of one or more aspects of Process 600, the addition offurther conditionals and operations, or the reorganization or separationof operations and conditionals into separate processes.

Process 600 begins at operation 601 where the control system 260determines a take-off event is occurring. A take-off event may includethe flight time period before the aircraft 100 reaches a cruisingaltitude, including taxiing to the runway and climbing to the cruisingaltitude. The control system 260 may determine a take-off event isoccurring in response to a user input or in response to a measurement ofoutput power from the aluminum-air fuel cell 120.

Before reaching a maximum power output point of the ascent, the aircraft100 can heat the aluminum-air fuel cell 120 r to increase the powerdensity of the aluminum-air fuel cell 120. In operation 603, the controlsystem 260 determines a prescribed temperature for the aluminum-air fuelcell 120. The prescribed temperature may be the temperature thatmaximizes the power density of the aluminum-air fuel cell 120.

In operation 605, the control system 260 operates the diverter system240 to transfer the waste heat from the waste heat source 105 to thealuminum-air fuel cell 120 outputting power during the take-off. Thecontrol system 260 allows the waste heat to heat the aluminum-air fuelcell 120 to the prescribed temperature. In some embodiments, the controlsystem 260 begins to transfer the waste heat to the aluminum-airfuel-cell 120 before completing operation 603.

In operation 607, the heated aluminum-air fuel-cell 120 provides outputpower to the propulsors of the aircraft 100. The increased temperatureof the aluminum-air fuel-cell 120 increases the maximum power outputmagnitude of the aluminum-air fuel cell 120.

It is contemplated that the various aspects, features, processes, andoperations from the various embodiments may be used in any of the otherembodiments unless expressly stated to the contrary. Certain operationsillustrated may be implemented by a computer executing a computerprogram product on a non-transient, computer-readable storage medium,where the computer program product includes instructions causing thecomputer to execute one or more of the operations, or to issue commandsto other devices to execute one or more operations.

While the present disclosure has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that only certain exemplary embodiments have been shown anddescribed, and that all changes and modifications that come within thespirit of the present disclosure are desired to be protected. It shouldbe understood that while the use of words such as “preferable,”“preferably,” “preferred” or “more preferred” utilized in thedescription above indicate that the feature so described may be moredesirable, it nonetheless may not be necessary, and embodiments lackingthe same may be contemplated as within the scope of the presentdisclosure, the scope being defined by the claims that follow. Inreading the claims, it is intended that when words such as “a,” “an,”“at least one,” or “at least one portion” are used there is no intentionto limit the claim to only one item unless specifically stated to thecontrary in the claim. The term “of” may connote an association with, ora connection to, another item, as well as a belonging to, or aconnection with, the other item as informed by the context in which itis used. The terms “coupled to,” “coupled with” and the like includeindirect connection and coupling, and further include but do not requirea direct coupling or connection unless expressly indicated to thecontrary. When the language “at least a portion” or “a portion” is used,the item can include a portion or the entire item unless specificallystated to the contrary. Unless stated explicitly to the contrary, theterms “or” and “and/or” in a list of two or more list items may connotean individual list item, or a combination of list items. Unless statedexplicitly to the contrary, the transitional term “having” is open-endedterminology, bearing the same meaning as the transitional term“comprising.”

Various embodiments of the invention may be implemented at least in partin any conventional computer programming language. For example, someembodiments may be implemented in a procedural programming language(e.g., “C”), or in an object oriented programming language (e.g.,“C++”). Other embodiments of the invention may be implemented as apre-configured, stand-along hardware element and/or as preprogrammedhardware elements (e.g., application specific integrated circuits,FPGAs, and digital signal processors), or other related components.

In an alternative embodiment, the disclosed apparatus and methods (e.g.,see the various flow charts described above) may be implemented as acomputer program product for use with a computer system. Suchimplementation may include a series of computer instructions fixedeither on a tangible, non-transitory medium, such as a computer readablemedium (e.g., a diskette, CD-ROM, ROM, or fixed disk). The series ofcomputer instructions can embody all or part of the functionalitypreviously described herein with respect to the system.

Those skilled in the art should appreciate that such computerinstructions can be written in a number of programming languages for usewith many computer architectures or operating systems. Furthermore, suchinstructions may be stored in any memory device, such as semiconductor,magnetic, optical or other memory devices, and may be transmitted usingany communications technology, such as optical, infrared, microwave, orother transmission technologies.

Among other ways, such a computer program product may be distributed asa removable medium with accompanying printed or electronic documentation(e.g., shrink wrapped software), preloaded with a computer system (e.g.,on system ROM or fixed disk), or distributed from a server or electronicbulletin board over the network (e.g., the Internet or World Wide Web).In fact, some embodiments may be implemented in a software-as-a-servicemodel (“SAAS”) or cloud computing model. Of course, some embodiments ofthe invention may be implemented as a combination of both software(e.g., a computer program product) and hardware. Still other embodimentsof the invention are implemented as entirely hardware, or entirelysoftware.

The embodiments of the invention described above are intended to bemerely exemplary; numerous variations and modifications will be apparentto those skilled in the art. Such variations and modifications areintended to be within the scope of the present invention as defined byany of the appended claims. It shall nevertheless be understood that nolimitation of the scope of the present disclosure is hereby created, andthat the present disclosure includes and protects such alterations,modifications, and further applications of the exemplary embodiments aswould occur to one skilled in the art with the benefit of the presentdisclosure.

What is claimed is:
 1. An aircraft, comprising: at least one of anaircraft motor or an aircraft motor drive positioned outside of afuselage of the aircraft; a metal-air fuel cell positioned inside thefuselage of the aircraft; a waste heat transfer system configured tothermally couple the metal-air fuel cell and the at least one of theaircraft motor or the aircraft motor drive; and a control systemconfigured to operate the waste heat transfer system to selectivelytransfer waste heat from the at least one of the aircraft motor or theaircraft motor drive to the metal-air fuel cell.
 2. The aircraft ofclaim 1, comprising an air supply system configured to pressurize an airsupply for the metal-air fuel cell.
 3. The aircraft of claim 1,comprising a plurality of metal-air fuel cells including the metal-airfuel cell, wherein the waste heat transfer system includes a divertersystem configured to selectively transfer the waste heat from the atleast one of the aircraft motor or the aircraft motor drive to a portionof the plurality of metal-air fuel cells.
 4. The aircraft of claim 3,wherein the control system is configured to determine a power outputstatus of a first metal-air fuel cell of the plurality of metal-air fuelcells, and to operate the diverter system to transfer the waste heatfrom the at least one of the aircraft motor or the aircraft motor driveto the first metal-air fuel cell in response to determining the poweroutput status, wherein the waste heat is configured to evaporate anelectrolyte of the first metal-air fuel cell.
 5. The aircraft of claim3, wherein the control system is configured to determine at least one ofa power output status or a temperature of one of the plurality ofmetal-air fuel cells, and to operate the diverter system to transferheat from the at least one of the aircraft motor or the aircraft motordrive to a first metal-air fuel cell in response to determining the atleast one of the power output status or the temperature.
 6. The aircraftof claim 1, wherein the control system is configured to determine atake-off event is occurring, wherein the control system is configured tooperate a diverter system to transfer heat from the at least one of theaircraft motor or the aircraft motor drive to the metal-air fuel cell inresponse to determining the take-off event is occurring.
 7. The aircraftof claim 1, wherein the waste heat transfer system includes aliquid-to-liquid heat exchanger, a liquid-to-air heat exchanger, and adiverter system, and wherein the metal-air fuel cell is an aluminum-airfuel cell.
 8. A method for heating a metal-air fuel cell, comprising:operating an aircraft including, at least one of an aircraft motor or anaircraft motor drive positioned outside of a fuselage of the aircraft,and a metal-air fuel cell positioned inside the fuselage of theaircraft; outputting power from the metal-air fuel cell; generatingthrust and waste heat using the at least one of the aircraft motor orthe aircraft motor drive; and transferring the waste heat to themetal-air fuel cell.
 9. The method of claim 8, comprising: pressurizingan air supply; and providing the pressurized air supply to the metal-airfuel cell.
 10. The method of claim 8, comprising determining at leastone of a power output status or a temperature, wherein transferring thewaste heat to the metal-air fuel cell is in response to determining theat least one of the power output status or the temperature.
 11. Themethod of claim 8, wherein the aircraft includes a second metal-air fuelcell.
 12. The method of claim 11, comprising: determining a power outputstatus of the second metal-air fuel cell; and transferring at least aportion of the waste heat to the second metal-air fuel cell.
 13. Themethod of claim 8, comprising: determining a power output status of themetal-air fuel cell; and evaporating an electrolyte using the waste heatof the metal-air fuel cell.
 14. The method of claim 8, wherein themetal-air fuel cell is an aluminum-air fuel cell.
 15. An aircraft,comprising: an aircraft motor; an aircraft motor drive; a firstmetal-air fuel cell configured to provide power to the aircraft motordrive; a second metal-air fuel cell configured to provide power to theaircraft motor drive; a waste heat transfer system configured tothermally couple the first and second metal-air fuel cells and at leastone of the aircraft motor or the aircraft motor driver; and a controlsystem configured to operate the waste heat transfer system toselectively transfer waste heat to the first metal-air fuel cell and thesecond metal-air fuel cell.
 16. The aircraft of claim 15, wherein thefirst and second metal-air fuel cells are aluminum-air fuel cells. 17.The aircraft of claim 15, wherein the waste heat transfer systemincludes a heater exchanger and a diverter system including a pluralityof valves, wherein the control system is configured to operate theplurality of valves to selectively transfer the waste heat to the firstmetal-air fuel cell, and then to the second metal-air fuel cell.
 18. Theaircraft of claim 15, wherein the control system determines a poweroutput status for the first metal-air fuel cell, and evaporates anelectrolyte of the first metal-air fuel cell in response to the poweroutput status.
 19. The aircraft of claim 15, comprising an air supplysystem configured to pressurize an air supply for the first and secondmetal-air fuel cell.
 20. The aircraft of claim 15, wherein the controlsystem is configured to determine a take-off event is occurring, whereinthe control system is configured to operate a diverter system of thewaste heat transfer system to transfer heat from the at least one of theaircraft motor or the aircraft motor drive to the first metal-air fuelcell in response to determining the take-off event is occurring.